<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
	<title>YUI Library Examples: Carousel Control: Using Ajax for deferred loading of items</title>
    

    <meta http-equiv="content-type" content="text/html; charset=utf-8">
    	<link rel="stylesheet" type="text/css" href="../../assets/yui.css" >

<style>
/*Supplemental CSS for the YUI distribution*/
#custom-doc { width: 95%; min-width: 950px; }
#pagetitle {background-image: url(../../assets/bg_hd.gif);}
</style>

<link rel="stylesheet" type="text/css" href="../../assets/dpSyntaxHighlighter.css">
<!--Script and CSS includes for YUI dependencies on this page-->
<link rel="stylesheet" type="text/css" href="../../build/carousel/assets/skins/sam/carousel.css" />
<link rel="stylesheet" type="text/css" href="../../build/button/assets/skins/sam/button.css" />
<script type="text/javascript" src="../../build/yuiloader/yuiloader-min.js"></script>
<script type="text/javascript" src="../../build/event/event-min.js"></script>
<script type="text/javascript" src="../../build/connection/connection-min.js"></script>
<script type="text/javascript" src="../../build/dom/dom-min.js"></script>
<script type="text/javascript" src="../../build/element/element-min.js"></script>
<script type="text/javascript" src="../../build/carousel/carousel-min.js"></script>
<script type="text/javascript" src="../../build/button/button-min.js"></script>


<!--begin custom header content for this example-->
<style type="text/css">
    /* Style the spotlight container */
    #spotlight {
        border: 1px solid #ccc;
        height: 240px;
        margin: 10px auto;
        padding: 1px;
        text-align: center;
        width: 240px;
    }

    #carousel {
        margin: 0;
    }

    #container {
        margin: 0 auto;
    }

    .yui-skin-sam .yui-carousel-nav ul,
    .yui-skin-sam .yui-carousel-nav select {
        display: none;
    }
    /* Always be sure to give your carousel items a width and a height */
    .yui-carousel-element li {
        height: 75px;
        width: 75px;
    }
</style>

<!--end custom header content for this example-->


<script type="text/javascript">
//enable passthrough of errors from YUI Event:
if ((typeof YAHOO !== "undefined") && (YAHOO.util) && (YAHOO.util.Event)) {
	YAHOO.util.Event.throwErrors = true;
}
</script>
</head>
<body id="yahoo-com" class="yui-skin-sam">
<div id="custom-doc" class="yui-t2">
<div id="hd">
	<div id="ygunav">
		<p><em><a href="http://developer.yahoo.com/yui/">YUI Library Home</a></em></p>
		<form action="http://search.yahoo.com/search" id="sitesearchform">
		<input name="vs" type="hidden" value="developer.yahoo.com">
		<input name="vs" type="hidden" value="yuiblog.com">
		<div id="sitesearch">
			<label for="searchinput">Site Search (YDN &amp; YUIBlog): </label>
			<input type="text" id="searchinput" name="p">
			<input type="submit" value="Search" id="searchsubmit" class="ygbt">
		</div>
		</form>	</div>
	<div id="ygma"><a href="../../"><img src="../../assets/yui.gif"  border="0" height="38"></a></div>
	<div id="pagetitle"><h1>YUI Library Examples: Carousel Control: Using Ajax for deferred loading of items</h1></div>
</div>
<div id="bd">
	
	<div id="yui-main">
		<div class="yui-b">
		  <div class="yui-ge">
			  <div class="yui-u first example">

    
	<div class="promo">
	<h1>Carousel Control: Using Ajax for deferred loading of items</h1>
	
	<div class="exampleIntro">
	<p>
    This example showcases the dynamic loading capabilities of the <a href="http://developer.yahoo.com/yui/carousel/">YUI Carousel Control</a>.  The YUI Carousel Control exposes an event called <code>loadItems</code>.  This
    event is fired whenever the Carousel needs items to be loaded into it for
    display.  Subscribing  to this event makes it easy to dynamically load
    the next set of images.
</p>
			
	</div>	
					
	<div class="example-container module ">
			<div class="hd exampleHd">
			<p class="newWindowButton yui-skin-sam"><!--<span id="newWindowLinkx"><span class="first-child">--><a href="csl_dynload2_clean.html" target="_blank">View example in new window.</a><!--</span></span>-->		
		</div>		<div id="example-canvas" class="bd">
	
		
	<!--BEGIN SOURCE CODE FOR EXAMPLE =============================== -->
	
	<!-- The Carousel container -->
<div id="container">
    <ol id="carousel"></ol>
</div>
<!-- The spotlight container -->
<div id="spotlight"></div>
<script>
    var curpos, items = [];

    function getImageTag(img) {
        return "<img src=\"" + img + "\" height=\"75\" width=\"75\">";
    }

    function getImages() {
        var carousel = this;
                
        YAHOO.util.Connect.asyncRequest("GET", "assets/php/getimages.php?pos="+curpos,
                {
                    success: function (o) {
                        var i = curpos,
                            j = 0,
                            r = eval('(' + o.responseText + ')');
                            
                        curpos += r.length;

                        while (i < curpos) {
                            if (r[j]) {
                                carousel.addItem(getImageTag(r[j]));
                            } else {
                                break;
                            }
                            i++;
                            j++;
                        }

                        carousel.set("selectedItem", carousel.get("firstVisible"));
                    },

                    failure: function (o) {
                        alert("Ajax request failed!");
                    }
        });
    }
                
    // Get the image link from within its (parent) container.
    function getLargeImage(parent) {
        var el = parent.firstChild;
                
        while (el) { // walk through till as long as there's an element
            if (el.nodeName.toUpperCase() == "IMG") { // found an image
                // flickr uses "_s" suffix for small, and "_m" for big
                // images respectively
                return el.src.replace(/_s\.jpg$/, "_m.jpg");
            }
            el = el.nextSibling;
        }
                
        return "";
    }

    YAHOO.util.Event.onDOMReady(function (ev) {
        var carousel, spotlight = YAHOO.util.Dom.get("spotlight");

        carousel = new YAHOO.widget.Carousel("container", {

             /* Setting numItems is required for dynamic loading. This property lets Carousel 
                know how many total items it will ever be populated with (statically and/or dynamically).
                Not to be confused with numVisible: the number of items shown to a 
                user per page. In this example, we don't specify numVisible and Carousel 
                defaults to 3 items visible per page. */
                 
                numItems: 17
        });
	
        YAHOO.util.Connect.asyncRequest("GET", "assets/php/getimages.php", {
                success: function (o) {
                    var i, r = eval('(' + o.responseText + ')');
                    
                    curpos = r.length;

                    for (i = 0; i < curpos; i++) {
                        items.push(r[i]);
                    }

                    // check if the Carousel widget is available
                    if (typeof carousel != "undefined") {
                        for (i = 0; i < curpos; i++) {
                            // if so, shove the elements into it
                            carousel.addItem(getImageTag(items[i]));
                        }
                        carousel.set("selectedItem", 0);
                        items = [];
                    }
                },

                failure: function (o) {
                    alert("Ajax request failed!");
                }
        });
                
        carousel.on("loadItems", function (o) {
            // more items available?
            getImages.call(this);
        });
                
        carousel.on("itemSelected", function (index) {
            // item has the reference to the Carousel's item
            var item = carousel.getElementForItem(index);

            if (item) {
                spotlight.innerHTML = "<img src=\""+getLargeImage(item)+"\">";
            }
        });
            
        carousel.render();
        carousel.show();
    });

</script>
	
	<!--END SOURCE CODE FOR EXAMPLE =============================== -->
	
		
		</div>
		
	
	</div>			
	</div>
		
	<h2 class="first">Making the Carousel Widget dynamically load images on the fly</h2>
<p>
    Here we will use the <a href="http://developer.yahoo.com/yui/carousel/">YUI Carousel Control</a>'s <code>loadItems</code> event to dynamically
    load the images on the fly.</p>
<p>
    This example has the following dependencies:
</p>

<textarea name="code" class="HTML" cols="60" rows="1"><link type="text/css" rel="stylesheet" href="http://yui.yahooapis.com/2.9.0/build/carousel/assets/skins/sam/carousel.css">
<script src="http://yui.yahooapis.com/2.9.0/build/yahoo/yahoo-dom-event.js"></script>
<script src="http://yui.yahooapis.com/2.9.0/build/element/element-min.js"></script>
<script src="http://yui.yahooapis.com/2.9.0/build/connection/connection-min.js"></script>
<script src="http://yui.yahooapis.com/2.9.0/build/carousel/carousel-min.js"></script></textarea>

<p>
    Initially we use <a href="http://developer.yahoo.com/yui/connection/">YUI Connection Manager</a> to load the initial set of items as
    soon as part of the DOM is visible.</p>

<textarea name="code" class="HTML" cols="60" rows="1"><div id="container">
  <ol id="carousel"></ol>
</div>
<!-- The spotlight container -->
<div id="spotlight"></div></textarea>

<p>
    We have a few simple CSS rules to set the dimensions for the Carousel items.
</p>

<textarea name="code" class="CSS" cols="60" rows="1">
/* Always be sure to give your carousel items a width and a height */
.yui-carousel-element li {
    height: 75px;
    width: 75px;
}</textarea>

<p>
    The YUI Carousel Control's constructor is passed <code>numItems</code> (the total number of items) so that it triggers the <code>loadItems</code> event if the items are not available.
    We'll use Connection Manager to load a set of items into the
    Carousel as early as possible.
</p>


<textarea name="code" class="JScript" cols="60" rows="1">YAHOO.util.Event.onDOMReady(function (ev) {
  var carousel, spotlight = YAHOO.util.Dom.get("spotlight");

  carousel = new YAHOO.widget.Carousel("container", {
      
  /* Setting numItems is required for dynamic loading. This property lets Carousel 
     know how many total items it will ever be populated with (statically and/or dynamically).
     Not to be confused with numVisible: the number of items to display
     per page. In this example, we don't specify numVisible and Carousel 
     defaults to 3 items visible per page. */
     
     numItems: 17
  });
  YAHOO.util.Connect.asyncRequest("GET", "php/getimages.php", {
      success: function (o) {
        var i, r = eval('(' + o.responseText + ')');
        curpos = r.length;

        for (i = 0; i < curpos; i++) {
          items.push(r[i]);
        }

        // check if the Carousel widget is available
        if (typeof carousel != "undefined") {
          for (i = 0; i < curpos; i++) {
            // if so, shove the elements into it
            carousel.addItem(getImageTag(items[i]));
          }
          carousel.set("selectedItem", 0);
          items = [];
        }
      },

      failure: function (o) {
        alert("Ajax request failed!");
      }
  });
});</textarea>

<p>
    The YUI Carousel Control exposes a <code>loadItems</code> custom event that is fired
    when the Carousel needs more items to be loaded.  This becomes very handy
    for us since we can subscribe to it and add more items in to the Carousel
    widget when required.
</p>

<p>
    In our case, the server program returns an array (JSON) of images.  This is
    parsed in the Ajax callback and then the Carousel's <code>addItem()</code> is called for
    every image.
     Apart from subscribing to this event, for displaying the selected image as a spotlight, we can subscribe to the <code>itemSelected</code> event that Carousel control exposes.
    This event is triggered whenever an item is selected and it returns the
    index of the selected item.  With the index of the item, we can use the
    Carousel's <code>getElementForItem()</code> API to get the reference to the Carousel's item (an <code>li</code> element in
    our case).
</p>
</p>


<textarea name="code" class="JScript" cols="60" rows="1">
carousel.on("loadItems", function (o) {
  // more items available?
  getImages.call(this);
});

carousel.on("itemSelected", function (index) {
  var item = carousel.getElementForItem(index);

  if (item) {
    spotlight.innerHTML = "<img src=\"" + getImage(item) + "\">";
  }
});

carousel.render();
carousel.show();

function getImageTag(img) {
    return "<img src=\"" + img + "\" height=\"75\" width=\"75\">";
}

function getImages() {
    var carousel = this;
                
    YAHOO.util.Connect.asyncRequest("GET",
				    "assets/php/getimages.php?pos="+curpos, {
            success: function (o) {
	        var i = curpos,
		    j = 0,
		    r = eval('(' + o.responseText + ')');
		
		curpos += r.length;
		
		while (i < curpos) {
		    if (r[j]) {
			carousel.addItem(getImageTag(r[j]));
		    } else {
			break;
		    }
		    i++;
		    j++;
		}
		
		carousel.set("selectedItem", carousel.get("firstVisible"));
	    },
					    
	    failure: function (o) {
	        alert("Ajax request failed!");
	    }
    });
}</textarea>

<p>
    The getLargeImage() function is quite easy to implement.  Since we have the
    reference to the Carousel's item, it is straightforward to implement a function that extracts the image within it.
</p>

<textarea name="code" class="JScript" cols="60" rows="1">// Get the image link from within its (parent) container.
function getLargeImage(parent) {
  var el = parent.firstChild;
  
  while (el) {  // walk through till as long as there's an element
    if (el.nodeName.toUpperCase() == "IMG") { // found an image
      // flickr uses "_s" suffix for small, and "_m" for big images respectively
      return el.src.replace(/_s\.jpg$/, "_m.jpg");
    }
    el = el.nextSibling;
  }
  
  return "";
}</textarea>

<h2>Configuration for This Example</h2>

<p>You can load the necessary JavaScript and CSS for this example from Yahoo's servers.  <a href="http://developer.yahoo.com/yui/articles/hosting/?connection&carousel&MIN#configure">Click here to load the YUI Dependency Configurator with all of this example's dependencies preconfigured</a>.</p>

				</div>
				<div class="yui-u">
						<div id="loggerModule" class="yui-skin-sam">
						<h3 class="firstContent">YUI Logger Output:</h3>
								<div id="loggerGloss"><p><strong>Note:</strong> Logging and debugging is currently turned off for this example.</p> 
							<p class="loggerButton"><span id="loggerLink"><span class="first-child"><a href="csl_dynload2_log.html">Reload with logging<br />
	 and debugging enabled.</a></span></span></p></div>
	
						</div>
					
				
					<div id="examples">
						<h3>Carousel Control Examples:</h3>
	
						<div id="exampleToc">
							<ul>
								<li><a href='../carousel/csl_selection.html'>Spotlight example</a></li><li><a href='../carousel/csl_circular.html'>Circular Carousel example</a></li><li><a href='../carousel/csl_reveal.html'>Partially revealing previous and next items</a></li><li><a href='../carousel/csl_imagentext.html'>Using both images and text within an item</a></li><li class='selected'><a href='../carousel/csl_dynload2.html'>Using Ajax for deferred loading of items</a></li><li><a href='../carousel/csl_dynloadandreplace.html'>Using deferred loading of items and Carousel's built-in paginator</a></li><li><a href='../carousel/csl_multirow.html'>Multi-row example</a></li><li><a href='../carousel/csl_paginationtemplate.html'>Pagination template example</a></li><li><a href='../carousel/csl_pagination.html'>Using Paginator with Carousel</a></li><li><a href='../carousel/carousel-ariaplugin.html'>Using the Carousel ARIA Plugin</a></li>							</ul>
						</div>
					</div>
					
					<div id="module">
						<h3>More Carousel Control Resources:</h3>
						<ul>
							<li><a href="http://developer.yahoo.com/yui/carousel/">User's Guide</a> (external)</li>
						<li><a href="../../docs/module_carousel.html">API Documentation</a></li>
                            
                            
							<li><a href="http://yuiblog.com/assets/pdf/cheatsheets/carousel.pdf">Cheat Sheet PDF</a> (external)</li></ul>
					</div>
			  </div>
		</div>
		
		</div>
	</div>


<div class="yui-b" id="tocWrapper">
<!-- TABLE OF CONTENTS -->
<div id="toc">
	
<ul>
<li class="sect first">Yahoo! UI Library</li><li class="item"><a title="The Yahoo! User Interface Library (YUI)" href="http://developer.yahoo.com/yui/">Home (external)</a></li><li class="item"><a title="The Yahoo! User Interface Blog" href="http://yuiblog.com">YUIBlog (external)</a></li><li class="item"><a title="YUILibrary.com hosts the YUI community forums" href="http://yuilibrary.com/forum/">YUI Discussion Forum (external)</a></li><li class="item"><a title="The YUI Library source can be checked out from GitHub" href="http://github.com/yui/">YUI on GitHub</a></li><li class="item"><a title="Instantly searchable API documentation for the entire YUI library." href="../../docs/index.html">API Documentation</a></li><li class="item"><a title="Examples of every YUI utility and control in action" href="../../examples/">Functional Examples</a></li><li class="item"><a title="Videos and podcasts from the YUI Team and from the Yahoo! frontend engineering community." href="http://developer.yahoo.com/yui/theater/">YUI Theater (external)</a></li><li class="item"><a title="YUI is free and open, offered under a BSD license." href="http://developer.yahoo.com/yui/license.html">YUI License (external)</a></li><li class="sect">YUI Functional Examples</li><li class="item"><a title="The YUI Animation Utility - Functional Examples" href="../../examples/animation/index.html">Animation</a></li><li class="item"><a title="The YUI AutoComplete Control - Functional Examples" href="../../examples/autocomplete/index.html">AutoComplete</a></li><li class="item"><a title="The YUI Browser History Manager - Functional Examples" href="../../examples/history/index.html">Browser History Manager</a></li><li class="item"><a title="The YUI Button Control - Functional Examples" href="../../examples/button/index.html">Button</a></li><li class="item"><a title="The YUI Calendar Control - Functional Examples" href="../../examples/calendar/index.html">Calendar</a></li><li class="selected "><a title="The YUI Carousel Control - Functional Examples" href="../../examples/carousel/index.html">Carousel</a></li><li class="item"><a title="The YUI Charts Control - Functional Examples" href="../../examples/charts/index.html">Charts</a></li><li class="item"><a title="The YUI Color Picker Control - Functional Examples" href="../../examples/colorpicker/index.html">Color Picker</a></li><li class="item"><a title="The YUI Cookie Utility - Functional Examples" href="../../examples/cookie/index.html">Cookie</a></li><li class="item"><a title="The YUI Connection Manager (AJAX) - Functional Examples" href="../../examples/connection/index.html">Connection Manager</a></li><li class="item"><a title="The YUI Container Family (Module, Overlay, Tooltip, Panel, Dialog, SimpleDialog) - Functional Examples" href="../../examples/container/index.html">Container</a></li><li class="item"><a title="The YUI DataTable Control - Functional Examples" href="../../examples/datatable/index.html">DataTable</a></li><li class="item"><a title="The YUI Dom Collection - Functional Examples" href="../../examples/dom/index.html">Dom</a></li><li class="item"><a title="The YUI Drag &amp; Drop Utility - Functional Examples" href="../../examples/dragdrop/index.html">Drag &amp; Drop</a></li><li class="item"><a title="The YUI Event Utility - Functional Examples" href="../../examples/event/index.html">Event</a></li><li class="item"><a title="The YUI Get Utility - Functional Examples" href="../../examples/get/index.html">Get</a></li><li class="item"><a title="The YUI ImageCropper Control - Functional Examples" href="../../examples/imagecropper/index.html">ImageCropper</a></li><li class="item"><a title="The YUI ImageLoader Utility - Functional Examples" href="../../examples/imageloader/index.html">ImageLoader</a></li><li class="item"><a title="The YUI JSON Utility - Functional Examples" href="../../examples/json/index.html">JSON</a></li><li class="item"><a title="The YUI Layout Manager - Functional Examples" href="../../examples/layout/index.html">Layout Manager</a></li><li class="item"><a title="The YUI Logger Control - Functional Examples" href="../../examples/logger/index.html">Logger</a></li><li class="item"><a title="The YUI Menu Control - Functional Examples" href="../../examples/menu/index.html">Menu</a></li><li class="item"><a title="The YUI Paginator - Functional Examples" href="../../examples/paginator/index.html">Paginator</a></li><li class="item"><a title="The YUI Profiler Utility - Functional Examples" href="../../examples/profiler/index.html">Profiler</a></li><li class="item"><a title="The YUI ProfileViewer Control - Functional Examples" href="../../examples/profilerviewer/index.html">ProfilerViewer</a></li><li class="item"><a title="The YUI ProgressBar Control - Functional Examples" href="../../examples/progressbar/index.html">ProgressBar</a></li><li class="item"><a title="The YUI Resize Utility - Functional Examples" href="../../examples/resize/index.html">Resize</a></li><li class="item"><a title="The YUI Rich Text Editor - Functional Examples" href="../../examples/editor/index.html">Rich Text Editor</a></li><li class="item"><a title="The YUI Selector Utility - Functional Examples" href="../../examples/selector/index.html">Selector</a></li><li class="item"><a title="The YUI Slider Control - Functional Examples" href="../../examples/slider/index.html">Slider</a></li><li class="item"><a title="The YUI Storage Utility - Functional Examples" href="../../examples/storage/index.html">Storage</a></li><li class="item"><a title="The YUI SWF Utility - Functional Examples" href="../../examples/swf/index.html">SWF</a></li><li class="item"><a title="The YUI SWFStore Utility - Functional Examples" href="../../examples/swfstore/index.html">SWFStore</a></li><li class="item"><a title="The YUI Stylesheet Utility - Functional Examples" href="../../examples/stylesheet/index.html">Stylesheet</a></li><li class="item"><a title="The YUI TabView Control - Functional Examples" href="../../examples/tabview/index.html">TabView</a></li><li class="item"><a title="The YUI TreeView Control - Functional Examples" href="../../examples/treeview/index.html">TreeView</a></li><li class="item"><a title="The YUI Uploader Utility - Functional Examples" href="../../examples/uploader/index.html">Uploader (experimental)</a></li><li class="item"><a title="The YUI YAHOO Global Object - Functional Examples" href="../../examples/yahoo/index.html">YAHOO Global Object</a></li><li class="item"><a title="The YUI Loader Utility - Functional Examples" href="../../examples/yuiloader/index.html">YUI Loader</a></li><li class="item"><a title="The YUI Test Utility - Functional Examples" href="../../examples/yuitest/index.html">YUI Test</a></li><li class="item"><a title="YUI Reset CSS - Functional Examples" href="../../examples/reset/index.html">Reset CSS</a></li><li class="item"><a title="YUI Base CSS - Functional Examples" href="../../examples/base/index.html">Base CSS</a></li><li class="item"><a title="YUI Fonts CSS - Functional Examples" href="../../examples/fonts/index.html">Fonts CSS</a></li><li class="item"><a title="YUI Grids CSS - Functional Examples" href="../../examples/grids/index.html">Grids CSS</a></li><li class="sect">YUI Articles on the YUI Website</li><li class="item"><a title="Answers to Frequently Asked Questions about the YUI Library" href="http://developer.yahoo.com/yui/articles/faq/">YUI FAQ (external)</a></li><li class="item"><a title="Yahoo!'s philosophy of Graded Browser Support" href="http://developer.yahoo.com/yui/articles/gbs/">Graded Browser Support (external)</a></li><li class="item"><a title="Reporting Bugs and Making Feature Requests for YUI Components" href="http://developer.yahoo.com/yui/articles/reportingbugs/">Bug Reports/Feature Requests (external)</a></li><li class="item"><a title="Serve YUI source files from Yahoo! -- free, fast, and simple" href="http://developer.yahoo.com/yui/articles/hosting/">Serving YUI Files from Yahoo! (external)</a></li><li class="item"><a title="Best practices for working with web services while protecting user privacy" href="http://developer.yahoo.com/security/">Security Best Practices (external)</a></li></ul>
</div>
</div>
	</div><!--closes bd-->

	<div id="ft">
        <p class="first">Copyright &copy; 2011 Yahoo! Inc. All rights reserved.</p>
        <p><a href="http://privacy.yahoo.com/privacy/us/devel/index.html">Privacy Policy</a> - 
            <a href="http://docs.yahoo.com/info/terms/">Terms of Service</a> - 
            <a href="http://docs.yahoo.com/info/copyright/copyright.html">Copyright Policy</a> - 
            <a href="http://careers.yahoo.com/">Job Openings</a></p>
	</div>
</div>
<script src="../../assets/syntax.js"></script>
<script src="../../assets/dpSyntaxHighlighter.js"></script>
<script language="javascript"> 
dp.SyntaxHighlighter.HighlightAll('code'); 
</script>

<script src='../../assets/YUIexamples.js'></script>


</body>
</html>
